A pixel driving circuit and a display panel are provided. The pixel driving circuit includes a data writing module, a data conversion module, and a current driving module. The data writing module is electrically connected to a first node and configured to transmit a data signal to the first node. The data conversion module is electrically connected to the first node, a second node, and a modulation signal source, and configured to generate a current driving control signal, and to output the current driving control signal to the second node. The current driving module is electrically connected to the second node, a light-emitting control wire, and a light-emitting device, and configured to control the light-emitting device to emit light. An effective pulse of the current driving control signal has different pulse widths in different gray-scale states.